1. Field of the Invention.
The present invention relates to inserts for securing threaded objects in wood and similar recipient materials.
2. Description of the Prior Art.
Inserts for permitting finely threaded objects to be secured to materials which are not suitable for direct threaded engagement are known in the art.
The principle for all inserts is that an insert is designed to be attached to a recipient material in the manner most appropriate for the particular material and for engaging an object which could not be effectively attached directly to the material. The insert can, therefore, act as an intermediary between the object and the recipient material for providing the most effective possible attachment of the object to the material.
Examples of this principle may be seen in the following U.S. Pat. No. 2,855,970 issued to R. Neuscholtz, No. 4,363,581 issued to J. Pease, No. 3,646,981 issued to Barnes, No. 4,440,534 issued to LaBate, No. 4,554,196 issued to Meeker, No. 4,556,350 issued to F. Bernhardt, et al., and No. 4,630,971 issued to T. Herbst, et al.
Presently, inserts for attaching bolts and "metal screws" to wood and wood-like materials are in the form of metallic cylindrical objects having external helical threads and each having a threaded axially-oriented columnar cavity for receiving the bolt or screw. The external threads of each insert are shaped and arranged as would be the threads of a wood screw. The threads in the columnar cavity are sized and shaped for engaging the particular bolt or screw that is to be attached to the recipient material. The inserts provide durable threaded orifices into and from which threaded objects may be repeatedly moved without substantial thread disfigurement.
A shortcoming of presently available wood inserts is that they are no more resistant to being removed from the wood than a common wood screw, because, having only threads to engage the wood, they are anchored in the same manner as wood screws. Therefore, wood inserts are frequently pulled by acute force from the hole in which they are installed, or are unscrewed by torque transferred to the insert by repeated installation and removal of a threaded object from the insert's threaded columnar cavity.
To combat the problem of unintentional removal of wood inserts, inserts are sometimes glued into their holes. Because direct bonding between the insert's metal and the surrounding wood is not particularly effective, the problem remains in large part even when the wood insert is glued.
An example of accidental removal of inserts posing a costly and time consuming problem in industry is in aircraft refitting where cabinets and equipment are attached to lightweight wood panels using inserts. When an insert is accidentally pulled or unscrewed from its recipient hole, the panel must often be replaced or a larger insert must be installed in the panel. Either way, significant time and expense is incurred for repair. The aircraft refitting industry in particular has long sought inserts which may be more reliably installed in wood panels.
It would, therefore, be desirable to design an insert for securing finely threaded objects to wood and wood-like materials, which insert would be designed for more effective anchoring against forces tending to separate it from its recipient material than presently-available inserts.